This application is based on Japanese patent application No. 2002-12997 filed in Japan on Jan. 22, 2002, the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method and an apparatus for forming an image on an image display medium.
2. Description of Related Art
In recent years, rewritable image display media called electronic paper or digital paper have been proposed as image display medium (image recording medium) for recording an image which can be used in place of normal papers.
Various types of image display media have been proposed. Among them, many image display media have a display layer whose optical characteristics (e.g., color, light transmittance and/or light reflectance when viewed from observation side) are varied, when an electric field is applied thereto, according to the direction/or intensity of the electric field.
An image is formed on the image display medium having such display layer as follows. For example, an electrostatic latent image corresponding to an image to be formed is formed on an image carrier such as a photosensitive member, and the electrostatic latent image is transferred to the image display medium.
Then an electric field is applied to the display layer using electrical charges of the electrostatic latent image on the image display medium, whereby the image is formed by changing the optical characteristics of the display layer.
Other proposed methods include, for example, a method comprising irradiating an surface of the image display medium with ions to form an electrostatic latent image corresponding to an image to be formed on the image display medium and applying an electric field to the display layer to form the image.
However, the above-mentioned image forming methods require a power source capable of generating a voltage of as high as several kV because the methods utilize electric discharge phenomenon in forming the electrostatic latent image.
Thus the image forming apparatus are expensive accordingly. Further the image forming apparatus handles a high voltage, necessitating use of an insulating material capable of withstanding high voltage. Moreover, the image forming apparatus may possibly need a special insulation measure. Large amounts of ozone and ions which deteriorate apparatus components may be generated due to the electric discharge.
An object of the present invention is to provide a method and an apparatus for forming an image on an image display medium having a display layer whose optical characteristics are changed by application of electric field, the method and apparatus being capable of forming the image without utilizing electric discharge phenomenon.
Another object of the present invention is to provide a method and an apparatus for forming an image on an image display medium having a display layer whose optical characteristics are changed by application of electric field, the method and apparatus being capable of forming the image at a low voltage and at a low cost without a need for a power source of high voltage.
A further object of the invention is to provide a method and an apparatus for forming an image on an image display medium having a display layer whose optical characteristics are changed by application of electric field, the method and apparatus being capable of suppressing generation of ozone and ions and being environmentally beneficial accordingly.
The invention provides a method of forming an image on an image display medium having a display layer whose optical characteristics are changed by application of electric field, the method comprising the steps of:
forming an electrostatic latent image corresponding to the image to be formed on a dielectric film having a plurality of float electrodes by injecting an electrical charge into at least one of the float electrodes; and
applying an electric field formed by the electrostatic latent image on the dielectric film to the display layer of the image display medium by bringing the electrostatic latent image formed on the dielectric film to a position opposed to the image display medium.
The invention also provides an apparatus for forming an image on an image display medium having a display layer whose optical characteristics are changed by application of electric field,
the apparatus comprising:
a dielectric film having a plurality of float electrodes formed thereon;
a device for forming an electrostatic latent image, the device being capable of forming the electrostatic latent image corresponding to the image to be formed on the dielectric film by injecting an electrical charge into at least one float electrode among the plurality of float electrodes; and
a device for applying an electric field formed by the electrostatic latent image on the dielectric film to the display layer of the image display medium by bringing the electrostatic latent image formed on the dielectric film to a position opposed to the image display medium.
The foregoing and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.